1. Field of the Invention
The present invention relates to a vibration actuator having a compact size, which is used as a vibration generator for notifying a user of an incoming call to a mobile wireless apparatus such as a mobile phone, or as a vibration generator for providing tactile sensation of a touch panel or the reality of a games machine to a user's finger or hand.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 10-117472 describes a technology in such a field. FIG. 1 of that publication illustrates a vibration actuator including a frame body and a soft elastic body that is fixed to the inner surface of the frame body. A cylindrical yoke, which is made of a magnetic substance, is disposed in the frame body. The yoke also serves as a weight for generating vibration, and is supported by a plate spring in the case. The plate spring has a shape like a conical spiral. The plate spring is fixed to a plate-shaped first elastic body that covers an opening of the case. An annular coil is inserted into the annular groove that is formed in an end face of the yoke. The coil is fixed to a plate-shaped second elastic body, which closes another opening of the frame body. An annular magnet is fixed to a wall of the groove. When an electric current having a predetermined frequency is applied to the coil of such a vibration actuator, the yoke, which functions as a weight, vibrates along the central axis, and the first and second elastic bodies resonate with each other at a desired frequency, whereby the frame body is vibrated in a desired manner (See Japanese Unexamined Patent Application Publication Nos. 10-117472, 2002-177882, 2003-24871, and 2002-200460.)